The preparation of methyl glyoxal acetals by reacting methyl glyoxal with alcohol in the presence of an acid catalyst is disclosed in U.S. Pat. No. 2,421,559. The required starting material for this synthesis, methyl glyoxal, is obtained by oxidation of acetone with selenium dioxide (U.S. Pat. No. 1,955,890), by partial oxidation of propylene glycol (U.S. Pat. No. 2,339,347), or by acid catalyst transformation of dihydroxyacetone (German Pat. No. 1,914,037; Great Britain Pat. No. 1,234,685 and U.S. Pat. No. 3,607,943). Still another process for preparing methyl glyoxal acetals requires the reaction of acetone with an alcohol and a nitrosating agent in the presence of an acid catalyst (U.S. Pat. No. 3,478,060).
U.S. Pat. No. 2,421,559 discloses that the omission of a water-immiscible organic solvent and the use of the monohydric alcohol as the solvent itself results in the formation of large amounts of undesired alkyl esters of an .alpha.-alkoxy propionic acid and methyl glyoxal dialkyl acetal dialkyl ketal.
The present one-step process which preferably employs an excess of alkanol surprisingly avoids producing these side or undesirable products. The compounds of the present invention are particularly valuable in the synthesis of growth promotants, for instance, in the synthesis of quinoxaline-di-N-oxide antibacterials.